The sentence you provided can be rephrased for clarity. Here are a couple of options:
1. "How am I considered a wife to someone I supposedly don't know about?"
2. "How can I be a wife to a man I’m unaware of?"
The meaning of this statement generally expresses confusion or disbelief. It suggests that the speaker is questioning how they can hold the title or role of a "wife" when they have no knowledge of the person they are supposedly married